Finite-size and pressure effects on the Raman spectrum of nanocrystalline anatase<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Ti</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Swamy, Varghese; Kuznetsov, Alexei; Dubrovinsky, Leonid; Caruso, Rachel A.; Shchukin, Dmitry G.; Muddle, Barry C.

doi:10.1103/physrevb.71.184302

Cited by 389 publications

(315 citation statements)

References 49 publications

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“…This gas phase process allows the preparation of bare and coated particles with a narrow particle size distribution. 10 As precursors butoxides ͓Ti-t-butoxide, Ti͑OC 4 H 9 ͒ 4 ; Hf-t-butoxide, Hf͑OC 4 H 9 ͒ 4 ; and Zr-t-butoxide, Zr͑OC 4 H 9 ͒ 4 ͔ and chlorides ͑TiCl 4 , HfCl 4 , and ZrCl 4 ͒ were used ͑Table I͒. In the process the water-free precursors were evaporated and transformed to oxides using a microwave plasma discharge and an Ar/ 20 vol % O 2 gas mixture as reaction gas.…”

Section: A Powder Synthesismentioning

confidence: 99%

Structure and grain growth of TiO2 nanoparticles investigated by electron and x-ray diffractions and Ta181 perturbed angular correlations

Schlabach

Szabó

Vollath

et al. 2006

Journal of Applied Physics

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Bare and coated TiO 2 nanoparticles with particle sizes d Ͻ 5 nm have been synthesized in a microwave plasma process. Structural properties of these materials have been investigated by transmission electron microscopy, x-ray diffraction, and perturbed angular correlation ͑PAC͒ measurements of the electric quadrupole interaction ͑QI͒ at the probe nucleus 181 Ta on the metal site of TiO 2 at temperatures 290ഛ T ഛ 1450 K. The electron diffraction of the uncoated nanoparticles in the as-synthesized state reflects long range order in the Ti sublattice. Depending on the particles size, either the anatase or the rutile phase of TiO 2 was found. Anatase appears to be the stable form of nanocrystalline TiO 2 below d ϳ 10 nm. The PAC spectra of these nanocrystalline oxides are characterized by a broad distribution of strong quadrupole interactions, indicating a strongly disordered oxygen environment of the metal sites. Upon annealing, the grain size grows from d Ͻ 5 nm after synthesis to d Ͼ 100 nm after 1300 K. PAC spectra taken in the same temperature range show that with increasing temperature, the initially disordered state transforms to well-ordered rutile TiO 2 . The data suggest a critical grain size of d ϳ 10 nm for the onset of the ordering process. The spectra of coarse-grained TiO 2 are reached at a particle size d ജ 30 nm. In n-TiO 2 coated with Al 2 O 3 and ZrO 2 both the cores and the coatings were found to grow with increasing temperature; the cores of the coated particles, however, grow much less than those of the noncoated particles. The PAC method was used to investigate the QI in both TiO 2 cores and in the ZrO 2 coating of n-TiO 2 / ZrO 2 at different temperatures. These data suggest that although the coated particles grow with temperature, the ordering process is obstructed, possibly by a solid state reaction between the TiO 2 kernels and the coatings.

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Section: A Powder Synthesismentioning

confidence: 99%

Structure and grain growth of TiO2 nanoparticles investigated by electron and x-ray diffractions and Ta181 perturbed angular correlations

Schlabach

Szabó

Vollath

et al. 2006

Journal of Applied Physics

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“…Among the several techniques used to characterize these materials, Raman spectroscopy plays a special role in the investigation of size effects on crystal vibrational properties in the nanometer scale. Depending on the crystal size nanocrystals undergo strain or nonstoichiometry which can significantly affect the Raman spectra [3,4]. Several reports on titanium dioxide nanocrystals show that Raman shift in this material is mainly due to phonon confinement (PC) effect [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

“…Agglomerates of nanosized TiO 2 crystals are promising materials for electrochemical, photochemical and photovoltaic applications [1][2][3][4]. Among the several techniques used to characterize these materials, Raman spectroscopy plays a special role in the investigation of size effects on crystal vibrational properties in the nanometer scale.…”

Section: Introductionmentioning

confidence: 99%

Effective Linewidth in Raman Spectra of Titanium Dioxide Nanocrystals

Salis¹,

Ricci²,

Anedda³

2009

Open Cond Matt Phy J

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Raman spectra of nanocrystals titanium dioxide are discussed and the correlation between the band shape of the allowed A 1g Raman mode and the crystals dimensions is discussed. Data on Raman spectra are reconsidered in the framework of a modified "hard confinement" model (MHC). The proposed model is based on the idea of using an effective linewidth parameter, which is a function of the effective dimension of the nanostructure, in spite of the intrinsic Raman band linewidth.The comparison with standard hard confinement model reveals better agreement with the experimental results for the MHC model up to 6 nm. Moreover, the analysis permits to improve the knowledge of the phonon dispersion curve as well as the intrinsic Raman bulk parameters. An analytical form of the size-dependent peak-position in nanocrystals, useful for an approximated size estimation, has been explicated. The general structure of the model permits to extended the MHC to other nano-sized materials.

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“…All the detected peaks were of the medium intensities. The peak corresponding to E g and A 1g modes of rutile vibration were observed in the sample heat treated at 750 o C and 900 o C [24]. But the relative error in the intensity of the peaks increased as the heating temperatures increased indicating completion in the formation of rutile phase at 900 o C with elimination of defects on the crystal structure.…”

Section: Resultsmentioning

confidence: 86%

Spectroscopic Investigation on Sol Gel Derived TiO<sub>2</sub> Nanoparticles

Singh¹,

Mukherjee²,

Ghosh³

et al. 2017

JAN

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Abstract. TiO 2 nanoparticles were synthesized by sol-gel method from titanium tetra isopropoxide. Influence of heat treatment on structural and morphological properties of TiO 2 nanoparticles was investigated by XRD and SEM. Spectral properties of the nanoparticles were investigated using FTIR, Raman spectroscopy, PL spectroscopy and UV-visible absorption spectroscopy. XRD analysis revealed the formation of mixed anatase and ruitle phase in the synthesized powder at 550 o C and existence of only rutile phase at 750 and 900 o C. The lattice parameters, crystallite sizes, volume of the unit cell, density and surface area of TiO 2 nanoparticles were determined from XRD analysis. SEM analysis showed that the prepared nanoparticles were in the nano regime, nearly spherical and larger agglomerated at lower temperature. EDX analysis showed that the TiO 2 composition obtained was near stoichiometric at lower temperature and the proportion of oxygen vacancy increased with the increase in temperature. The presence of Ti-O and Ti-O-Ti bonds was confirmed by FTIR spectra. PL spectroscopy showed that the change in surface states and presence of anatase and rutile phases of TiO 2 were also responsible for exhibiting the change in PL intensity. UV-visible absorption spectra showed the shifting of absorption edge towards the higher wavelength with the increase in temperature while the corresponding energy band gap of semiconductor nanoparticles decreased. Change in Raman spectra with the increase in temperature was observed due to anatase to rutile phase transformation and with the increase in the particle size.Keywords: TiO 2 nanopowder, sol-gel, annealing, spectroscopic properties. IntroductionTitania nanoparticles have important applications in the field of optical devices, sensor and photocatalysis [1,2]. These nanoparticles have different electrical, optical and magnetic properties compared to their bulk counterparts due to large surface to volume ratios and quantum size effect [3]. There are several factors in determining the important properties like, particle size, crystallinity and morphology that affect the performance of TiO 2 in applications [4][5][6]. TiO 2 as a wide indirect band gap n-type semiconductor and generally exist in the three polymorphs of TiO 2 are anatase (I4/amd), rutile (P42/mnm) and brookite (Pcab). Brookite exists in an orthorhombic structure while anatase and rutile both possess tetragonal unit cells. Among these, anatase is metastable at lower temperature and has excellent chemical and physical properties for environmental purification, although rutile is the more stable phase from thermodynamic point of view. The phase composition has significant effect on the properties and performance of nano TiO 2 and therefore it is desirable to control the transformation to develop a particular phase or phase mixture subsequent to thermal treatment. The phase transformation depends on the growth process affected by defect concentration, grain boundary concentration and particle packing as well [7][8][9]. ...

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Finite-size and pressure effects on the Raman spectrum of nanocrystalline anataseTiO2

Cited by 389 publications

References 49 publications

Structure and grain growth of TiO2 nanoparticles investigated by electron and x-ray diffractions and Ta181 perturbed angular correlations

Structure and grain growth of TiO2 nanoparticles investigated by electron and x-ray diffractions and Ta181 perturbed angular correlations

Effective Linewidth in Raman Spectra of Titanium Dioxide Nanocrystals

Spectroscopic Investigation on Sol Gel Derived TiO<sub>2</sub> Nanoparticles

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